Filed under: 3D, Guest Blogger, On Location, photogrammetry, Training, Workshops
In October 2019, our training team at CHI delivered a 4-day photogrammetry class for staff at the Library of Congress (LoC) in Washington, D.C. The class was part of a pilot project to test the use of photogrammetry for building digital models of three-dimensional items held in the Library’s collections. Eileen Jakeway, innovation specialist in Digital Strategy at the LoC, wrote a blog about it. Check it out!
The Library also released some 3D models, including a cast of Abraham Lincoln’s hand (this is CHI’s snapshot of the model).
Filed under: RTI, Training, Workshops | Tags: Digital Imaging, RTI, RTIViewer, Training, Workshops
Marlin Lum is the Imaging Director at Cultural Heritage Imaging (CHI) and a member of the CHI training team.
I thought I’d take a few moments to decode what it’s like to be an instructor in one of our RTI training classes. Like anything else, there’s a certain level of planning, intention, and positive enthusiasm that I expect from myself (and from anyone enrolled). I do my best to pass this on to everyone who elects to give us their valuable time. I truly enjoy teaching at this level. I see these training sessions as a unique opportunity to pass on my knowledge in a form that can help create conditions primed for discoveries as well as to make new friends.
RTI capture with iPhone in tow to track one of those special photographic moments. (Aviator sun glasses optional.)
CHI RTI training (as well as our photogrammetry class) simply means spending four days conveying photo DIY geekiness to a usually very enthusiastic, and sometimes even rowdy, motley crew of professors, scholars, conservation professionals, archaeologists, and pro photographers. (By the way, just so you know, it’s usually the archaeologists and the pro shooters who can hold the most liquor.) All of these folks, and everyone who walks into one of our trainings, is ultra-talented, focused, and very motivated to succeed. As you might guess, this makes my job significantly easier as well as seemingly more important. At least the furious note-taking in most of my hands-on demos would lead me to think this. As I always state on day one, hour one: “I make it my goal to make you successful (at least photographically).”
Got spheres? Get on the plane! Make sure those spheres are on same plane as the object. Place them carefully so they do not move and are always in focus.
Helping these trainees from the bus stop to the f-stop and along their way to making discoveries is not only a privilege but something of a rush. More than once I have witnessed the birth of an important discovery. I once watched a conservator realize that a Mayan lead ingot sitting on the bench actually had numerous coded “knot” inscriptions, though they were seemingly invisible to the human eye. RTI revealed this fairly matter of factly. I’ve heard the shriek of conservation staff as RTI revealed a previously hidden but somewhat “suspect” under-painting. I once heard an Egyptologist glyph expert read aloud, then carefully re-read, a good fortune spell. Apparently, the original person who had paid for the spell got taken, because RTI revealed that the original owner’s name had been scratched away and re-etched with a new dude’s name. I imagine that was a fairly common event. Wait till the guy dies, then sneak over there, scratch out his name, and write yours. Boom, check, all done, sweetie. All right there in stone — can’t deny that when the judge points a finger at you. The oohs and aahs I hear never disappoint.
Setting up the object for proper RTI capture can take a bit of time, but using Live View mode can help your troubles go away.
Here’s the gist: I get fired up when I see you guys get fired up. RTI has the potential to inspire. Materials and objects that you didn’t think were worth imaging suddenly land on the request list. One down side: I heard a pro shooter from a large institution complain that he didn’t need any more work (oh, sorry).
Use the RTIViewer to look at the details.
Just recently we taught an RTI class at the CHI studio (the photos in this blog are from that class). I’m not sure that any real discoveries were made, because we don’t have glyphs, ancient relics, masterpieces, or any “weird” non-provenance stuff from eBay lying around. However, I can vouch for the fact that I had a great time meeting cool new professionals, watching them engaged in what they do best, and then seeing them walk out the door, doing it better than before. Yup, I did write that. It’s in our best interest at CHI to make sure that you’re successful taking RTI (or photogrammetry) back to your professional crew.
Filed under: Equipment, Guest Blogger, photogrammetry, Technology, Training, Workshops
Christopher Ciccone is a photographer at the North Carolina Museum of Art, and this is a post he wrote for the museum’s blog Circa. Chris attended the 4-day photogrammetry training class taught by the CHI team at the museum in May 2018 and describes the experience here. Thank you for sharing your blog, Chris!
Photogrammetry is the science of making measurements from photographs of an object (or in aerial photogrammetry, a geographic area). This is done by taking a series of carefully plotted still photographs that incorporate targets of known size and then analyzing the images with specialized software. The resulting data can then be used to generate a variety of output products such as maps, detailed renderings, and 3-D models for use in a number of applications.
Dense point cloud rendering of sculptor William Artis’s Michael. The blue rectangles represent the position of the camera for each image that was used to create the 3-D model.
Although photogrammetry as a scientific measurement technique has existed since the nineteenth century, it has been the advent of digital photography and high-powered computational capacity that has made it a practical tool for scholars, researchers, and photographers. Because photogrammetry can be employed on objects of any size, its usefulness in the cultural heritage sector is vast. Interesting uses of photogrammetry include, for example, documentation of historic sites that might be slated for destruction or are in danger of ongoing environmental damage.
Workshop participants in the NCMA Park photograph various angles of Ledelle Moe’s Collapse.
Photogrammetry at the NCMA
In May the Musem’s Photography and Conservation departments hosted instructors Carla Schroer and Mark Mudge from Cultural Heritage Imaging in San Francisco for a four-day photogrammetry training workshop. Participants included myself, NCMA Head Photographer Karen Malinofski, and NCMA objects conservator Corey Riley, as well as colleagues from the National Park Service and the University of Virginia.
Workshop participants Cari Goetcheus and Gregory Luna Golya photograph Willam Artis’s Michael on a turntable to facilitate views from all angles of the object.
William Ellisworth Artis, Michael, mid-to-late 1940s, H. 10 1/4 x W. 6 x D. 8 in., terracotta, Purchased with funds from the National Endowment for the Arts and the North Carolina State Art Society (Robert F. Phifer Bequest)
In the course of the class, we photographed several artworks in the Museum’s permanent collection, from a small bust by William Artis to Ledelle Moe’s monumental outdoor sculpture Collapse. The technique consisted of taking “rings” of overlapping photographs around the object, at optimal distance relative to focal length, with camera lenses set at a fixed focus point and aperture. The primary objective in each case was to establish a consistent, rule-based workflow in order to reduce the measurement uncertainty of the rendered photoset, which may then be used to generate reliable 3-D data as well as be archived and used for further study by others.
At the NCMA we plan to employ the technique for such projects as monitoring the surface wear over time of our outdoor sculptures, revealing surface markings of ancient objects for insight into makers’ techniques and tools, and generating 3-D renderings of delicate artifacts that can be manipulated and viewed in virtual environments by museum visitors and scholars. Other applications will become possible as 3-D processing tools are improved.
Will Rourk of the University of Virginia and NCMA Head Photographer Karen Malinofski photograph details of Collapse.
Christopher Ciccone is a photographer at the North Carolina Museum of Art.
Filed under: Guest Blogger, Technology, Training, Workshops | Tags: 3D data, conservation, photogrammetry, Training
Lauren Fair is Associate Objects Conservator at Winterthur Museum, Garden, & Library in Buffalo, New York. She also serves as Assistant Affiliated Faculty for the Winterthur/University of Delaware Program in Art Conservation (WUDPAC). Lauren was a participant in CHI’s NEH grant-sponsored 4-day training class in photogrammetry, August 8-11, 2016 at Buffalo State College. She posted an account of her experience in the class in her own blog, “A Conservation Affair.” Here is an excerpt from her fine post.
I have discovered the perfect way to decompress after a four-day intensive seminar on 3D photogrammetry: go to your friend’s cabin on a small island in a remote part of Canada. While you take in the fresh air and quiet of nature, you can then reflect on all that you have shoved into your brain in the past week – and feel pretty good about it!
The Cultural Heritage Imaging (CHI) team – Mark, Carla, and Marlin – have done it again, in that they have taken their brilliance and passion for photography, cultural heritage, and documentation technologies, and formulated a successful workshop on 3D photogrammetry that effectively passes on their expertise and “best practice” methodologies.
The course was made possible by a Preservation and Access Education and Training grant awarded to CHI by the National Endowment for the Humanities.
(Read the rest of Lauren’s blog here.)
Filed under: Guest Blogger, Technology, Training | Tags: 3D data, conservation, photogrammetry, Training
Our guest blogger, Emily B. Frank, is currently pursuing a Joint MS in Conservation of Historic and Artistic Works and MA in History of Art at New York University, Institute of Fine Arts. Thank you, Emily!
I’ve been following the development and improvement of photogrammetry software for the past few years. As an objects conservation student with a growing interest in the role of digital imaging tools in the study and conservation of art, I’ve always found photogrammetry of theoretical interest. In my opinion, until recently the limited accuracy of the software and tools impeded widespread applications in conservation. With recent advances, this is no longer the case; sub 1/10th mm accuracy has changed the game.
This January, the stars aligned and I was able (and lucky) to participate in CHI’s January photogrammetry training. From January 11 to 14, I lived and breathed photogrammetry in CHI’s San Francisco studio. The four-day course was co-instructed by Carla Schroer, Mark Mudge, and Marlin Lum, who each brought something extraordinary to the experience.
CHI’s January 2016 photogrammetry class: blogger Emily Frank is fourth from the right.
For those of you that don’t know them personally, I’ll provide context; these guys are total gurus. Carla brings business and tech know-how from years of work in Silicon Valley earlier in her career. She has a warm and direct teaching style that is accessible no matter what your photography/imaging background. Mark is a true visionary; he is rigorous and inventive, and always carefully pushing the brink of what’s possible. Marlin is the photographer of the group and a master at fabricating the perfect tool/workstation for the capture of near-perfect source images. His never-ending positivity is contagious. Together they are practically unstoppable. It’s obvious that they love teaching and truly believe in the power of the tools they are sharing.
The class began with a brief theoretical introduction, then dove into practical aspects of capture and processing. We swiftly covered how to approach a range of situations, what equipment to use, where to compromise, and where to stick to a specific protocol, etc. We focused on methodology, and we practiced a lot. We moved through capture and processing of increasingly complex projects, and we received detailed handouts to supplement everything we were learning. The class also afforded students the opportunity to work on a larger group project; this January we captured a 3D model of a reproduction colossal Olmec head located outdoors at City College of San Francisco. CHI focuses on repeatability and process in order to achieve a robust, reproducible result.
Setting up for image capture at the January 2016 photogrammetry class; blogger Emily Frank is far left.
An added benefit of the class was the insight gained through conversation with the other students, who included museum photographers, landscape photographers, archaeologists, classicists, 3D-imaging academics, and the founder of a virtual reality start-up. This diversity fostered a breeding ground for inventive implementation, and the inevitable collaboration left me envisioning new ways to employ photogrammetry as a tool in my work.
For those of you who have ever considered the use of photogrammetry, I would strongly encourage you to sign up for one of CHI’s upcoming trainings. I still have a lot to learn and master, but I left the training with the feeling that with practice I would be able to capture and process 3D data with the accuracy and resolution to meaningfully contribute to the academic study of works of art.
Notes from CHI:
- Emily Frank has included a link to a 3D model of a reproduction colossal Olmec head located at City College of San Francisco. This huge outdoor sculpture was a practice subject in CHI’s January photogrammetry class in which our guest blogger Emily Frank was a participant. The model was created with photogrammetry, and it is presented on Sketchfab, a website for 3D models.
- See our Flickr photo album of the January 2016 photogrammetry class in which blogger Emily Frank participated.
Filed under: Commentary, News, Training | Tags: glossary of terms, photographic terms, technical terms
Over the years we have received a lot of requests for a glossary of terms used in RTI, and we are happy to announce that a new “Glossary of Photographic and Technical Terms for RTI” is available on our website! It includes photographic terms you need to know for RTI, like “Depth of Field,” “Color Temperature,” and “Aperture.” Also included are technical terms from computer graphics and computer vision like “BRDF,” “Fitting Algorithm,” and “Phong Lighting Model.” We have included terms for file formats like DNG, XMP and TIFF, along with basics in multi-spectral imaging such as “Infrared” and “Ultraviolet-induced Visible Fluorescence Photography.” We also included terms related to keeping good process history in your RTI work, including “Digital Lab Notebook,” “ICOM-CIDOC,” and “Empirical Provenance.” We did our best to adapt the definitions for RTI users, and we also included a few notes and recommendations on photographic settings.
As always with our work at CHI, this project was a collaboration. Lots of folks offered terms they wanted to see defined, and some provided definitions. We especially want to thank Tom Malzbender for definitions for many of the technical terms; Yosi R-Pozeilov for sharing his extensive glossary of photographic terms; and technical writer Judy Bogart for pulling it all together. And finally, we had a wee bit of funding for this work from the Institute of Museum and Library Services, as part of a larger grant project in their 21st Century Museum Professionals grants. Much of the work was done through volunteer efforts.
If you value this kind of documentation, along with the free open source RTI software, please consider making a donation to help support it.
This week we are rolling out CHI’s new free forums for the community of people who are developing and adopting Reflectance Transformation Imaging (RTI) and related computational photography. We have had the idea to do this for some time, and after trying a couple of different forum software packages, getting input from friends, and tinkering with some of the forums setup, we are now ready to invite the larger community. Join us! Sign up for a forums account now: go to http://forums.culturalheritageimaging.org and click the link “Sign In” in the upper right of the window to begin setting up your new account. You can look at content in the forums without an account, but a free account is required to post there (this is to keep the spammers at bay).
As our RTI training has expanded, and more people are adopting RTI, we are frequently asked how users can see what other people are doing with the technology, and whether CHI offers a place to find answers when difficulties arise. We know many people want to keep up with the latest news on software releases, equipment, and related topics. Our forums were created to answer these needs. We hope to see the RTI community help each other and share their experiences and insights.
I’d like to say thank-you to those who made this new forums service possible. First, thanks to the Institute of Museum and Library Services (IMLS) because we were able to use a little funding from our 21st Century Museum Professionals grant to get the forums going. This grant, which has enabled 10 4-day training sessions in RTI — we just finished the 9th one this month — has also helped us support updates to our software, user guides, and other materials associated with the adoption and use of RTI at museums and libraries. Sarah Ross did a fine job installing and setting up the forum software for us! The team at CHI has already added content to get the forum going and answered questions that have come in. We have had a great group of beta testers who tried this out, posted content, and gave us feedback.
We hope that you, members of our community, will engage in the forums, asking and answering questions to help each other. This is just the beginning; we plan to expand the forums to cover additional topics as the need arises. Please write to us and let us know what you want from the forums: what will make them the truly useful for you? Send your comments or questions in an email to: forums at culturalheritageimaging.org
Filed under: Commentary, Training, Uncategorized | Tags: ACR, batch, processing, zero, zero out
During the post processing phase, when you open your DNG files in Adobe Camera Raw (ACR), you have an opportunity to adjust your white balance and your exposure compensation. Prior to making these adjustments …
We recommend that you create a “Zeroed Out Settings” custom preset, and apply it to the entire image set. Consider making this your default preset for Adobe Camera Raw. To do this, set all of the settings to 0, then save as a named preset using the flyout menu for the Basic image adjustments panel. In particular, make sure all sharpening options are set to 0.
Make sure that your Zero Out Settings match the above screen shot (click image).
Check the settings in all of the tabs. The first three tabs (Basic, Tone Curve, and Detail) have default settings that are non-zero; the radius setting on the Detail tab cannot be less than 0.5. In other tabs, default settings are already zero. (as taken from page 5 in the RTI Highlight Processing Guide v1.4)
‘Zeroing Out’ data ensures that your data is not being processed, interpreted or stylized to fit consumer tastes.
In July we were back at the Worcester Art Museum Conservation lab to give a training in our IMLS sponsored 21st Century Museum Professionals program. The Worcester conservation team was the first conservation lab to see the potential for Reflectance Transformation Imaging for art conservation back in 2006. We built a lighting array for them, and delivered it and a training in May of 2008.
It was great to be back with that team and to see a bit of what they have been up to. We were really impressed with their RTI work on Greek Vases. They gave us permission to post a paper about this work so others in the RTI community can see it.
See below for more information on the publication:
An Evaluation of Decorative Techniques on a Red-Figure Attic Vase from the Worcester Art Museum using Reflectance Transformation Imaging (RTI) and Confocal Microscopy with a Special Focus on the “Relief Line”
Authors: Paula Artal-Isbrand(1), Philip Klausmeyer(2), Winifred Murray(3); 1,2,3 Worcester Art Museum, 55 Salisbury Street, Worcester, MA 01609, U.S.A.
ABSTRACT
Decorative features on a Greek red-figure stamnos in the collection of the Worcester Art Museum were examined using Reflectance Transformation Imaging (RTI) and scanning laser confocal microscopy. These two surface examination tools helped to answer questions relating to the decorative process, particularly the tools and techniques that Attic painters used to create the so-called glossy black “relief lines” and “relief dots.” This research also incorporated fabricated mock-ups to help understand the ancient technology. It was determined that the relief line was not produced by an extruded method, but with a brush made of one or very few hairs, an idea first proposed by Gérard Seiterle in 1976 and termed Linierhaar. It was observed that not one but two distinct types of relief lines exist: the “laid” line (proposed by Seiterle) characterized by a ridge running through the middle of the line and the “pulled” line (proposed in this paper) which has a furrowed profile. Both line types were reproduced with a Linierhaar. Additionally, relief dots were replicated using a conventional brush. Surface examinations of other red-figure vessels using RTI and the confocal microscope suggest these conclusions apply to vessels of this genre as a whole.
Download the Publication: An Evaluation of Decorative Techniques on a Red-Figure Attic Vase from the Worcester Art Museum using Reflectance Transformation Imaging (RTI) and Confocal Microscopy with a Special Focus on the “Relief Line”
Thanks again to the team at Worcester for their wonderful hospitality and collaborative spirit! Keep up the great work.
June 8, 2011
Buzzed at AIC
At the recent annual meeting of the American Institute for Conservation (AIC) in Philadelphia, I was happy to see both past and future participants in the IMLS-sponsored CHI RTI training session program. I had to break the news to some interested parties that the sessions at the Worcester Art Museum and at the San Francisco Museum of Modern Art are already filled (with waiting lists) – but a few openings remain (apply here) in the sessions scheduled for the Smithsonian’s Museum Conservation Institute and the Indianapolis Museum of Art. Since AIC, several spots have already been taken.
Of course, conservators always want more visual information, and have been quick to understand the benefits of RTI for their work. Once conservators attend a CHI training session, RTI adoption spreads throughout the conservation community. At AIC, I heard several tales of conservators reaching out to their curatorial colleagues, presenting the extremely detailed technical art historical information to be gained from RTI. Curators were impressed! The ability to acquire this kind of detail is one of the hallmarks of RTI – in fact, in CHI’s Kress video Debbie Evans (paper conservator, Fine Arts Museums of San Francisco) mentions that RTI can allow the conservator to provide this important, detailed information to the curator. We look forward to more wonderful conservator/curator interactions!
By Elizabeth Peña
Cultural Heritage Imaging 